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Topic: Micro four DoF and lenses (Read 10622 times)

I am really attracted by 4/3 system as it is small. I believe in few years the cameras will come with great sensors and IQ that will be good for my needs. Per Dxo olympus om has a slighty better dynamic range than 5d iii at the moment.What do you think about a future of the lenses.Why there's no lenses like 85mm f/1.2. The eqvivalent on 4/3 would be 42.5mm f/0.6, right?

« Last Edit: January 19, 2013, 05:57:11 PM by mirekti »

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M240 | 35mm FLE | 75mm Cron | 135mm APO

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The one down side of the m4/3rd systems is you'll never get the shallow DOF you can with full frame cameras, or even APS-C for that matter. The fastest lenses made right now are f/1.7, and that would be equal to about f/3.5 on a full frame camera. The idea of getting anywhere close to the DOF you have with f/1.2, or even f/2.0, on a full frame camera is just not going to happen.

The upside is if you shoot at f/1.7-f/2.0 on m4/3 you'll get decent amount of subject in-focus, so there is an advantage in that direction, essentially giving you better low light capabilities. You can shoot a group shot at f/2.0 on an OMD camera at ISO 3200 and get the same shot essentially as you would at f/4.0 & ISO 6400 on a full frame, with the same shutter speed or flash output.

The other nice thing with the OMD is every lens is image stabilized, including the fast primes. It's a fantastic camera, probably ahead of it's time as I'm sure a lot of features on it will be found on most cameras of the future. The biggest knock I've heard about it is the AF isn't particularly good for fast moving subjects, or for very dark situations. That said, there are two great advantages to the AF, when it does lock on it's very reliable and perfectly in focus, and there is no issue with lens calibration, no problems with back/front focus. With time, the CDAF system it employs may prove to be the best AF system ever, once they get it working better with fast moving subjects and dark shooting conditions, both problems are probably just a matter of time to improve upon, requiring improved image gain for low light and fast processing abilities for moving subjects.

The one down side of the m4/3rd systems is you'll never get the shallow DOF you can with full frame cameras, or even APS-C for that matter. The fastest lenses made right now are f/1.7, and that would be equal to about f/3.5 on a full frame camera. The idea of getting anywhere close to the DOF you have with f/1.2, or even f/2.0, on a full frame camera is just not going to happen.

f/0.95 is the fastest lens I've ever heard of, and generally they are not optimal performers, reading the review of the Voigtlander confirms this, sounds like you want to use it at f/2.0 or higher, might as well get the Olympus lens instead, at least you get AF. If they could make an f/0.6-0.7 lens, I can't imagine it would be very good.

The fastest lens, AFAIK, is the Zeiss Planar 50mm f/0.7. They made only 10, and the cost was astronomical - literally: NASA bought six for the Apollo lunar program. Stanley Kubrick bought three for candlelit filmmaking (Barry Lyndon), and Zeiss kept the last one - they've displayed it at Photokina.

I am really attracted by 4/3 system as it is small. I believe in few years the cameras will come with great sensors and IQ that will be good for my needs. Per Dxo olympus om has a slighty better dynamic range than 5d iii at the moment.What do you think about a future of the lenses.Why there's no lenses like 85mm f/1.2. The eqvivalent on 4/3 would be 42.5mm f/0.6, right?

At the present time the E-M5 gives superior IQ to the entire Canon APS-C line, but inferior to any of the FF Canons. A couple of years ago, the Oly IQ was far inferior to the Canon APS-C... which shows the work they have put into it. The Olympus E5, alledgedly thier flagship 4/3 body, is way back and it is almost certain that the 4/3 line is dead as no cameras or lenses have been released in about 2 1/2 years....

The selection of m4/3 lenses continues to improve.... lots of short ones but very little selection in long glass, and no long primes.... unlike the Canon selection of M lenses at 2

Personally, If I were to run out today and buy a mirrorless, it would be the E-M5... but I am not ready to go that route yet...

I am really attracted by 4/3 system as it is small. I believe in few years the cameras will come with great sensors and IQ that will be good for my needs. Per Dxo olympus om has a slighty better dynamic range than 5d iii at the moment.What do you think about a future of the lenses.Why there's no lenses like 85mm f/1.2. The eqvivalent on 4/3 would be 42.5mm f/0.6, right?

The micro 4/3 lenses focus closer than the full frame "equivalents". For example, the 45mm f/1.8 focuses at 0.5m, so its dof at MFD is about 1cm (or less than half an inch). The 75mm f/1.8 focuses at 84cm and dof is about 1/4 of an inch at that distance and less than an inch at a more reasonable shooting distance of 5ft (about what you'd use for a typical head shot)

Of course all your EF lenses will work on micro 4/3 and give the same dof as they do on FF (though with a cropped field of view).

The biggest obstacle would be the price for selling it. The 0.95 lens we have today costs about 10000$. 0.6 would be like..100.000$ or maybe more Whos gonna buy that for a 4/3 system? ^^ And enjoy the 1/8000 or faster shutter speed you will need if you use it wide open in the sun outside. Permanent ND filter needed indoors probably And i dont wanna even think how shallow the DOF would be. Eyeball in focus, eyelashes blurry much

It might help to add a quick primer on the meaning of f/ numbers and aperture and focal length and the rest.

It's pretty simple, really.

Starting with focal length...well, it's an intrinsic property of the lens. The full, unadulterated explanation can get quite convoluted, especially when you get into telephoto and retrofocus lenses and the like...but the intuitive explanation is that, if you hold a cutout the same size as your sensor the same distance from your eyeball as the lens's focal length, the field of view is the same. That is, take a piece of paper, cut out a 24mm x 36mm rectangle in it, and hold the paper 50mm from your eye and what you see in that hole will be the same framing as a 50mm lens on a full-frame camera. Now, move the paper closer, hold it 24mm away, and you'll see the same framing as a 24mm lens. Hold it really far away, 300mm, and you'll see what a 300mm lens would see.

You know how pinhole cameras work? That just that tiny little hole is enough to project an image, even though it's not especially sharp? Well, every hole actually is a pinhole camera -- that's why shadows during an eclipse become crescent-shaped. The aperture of a lens is the diameter of the hole in the lens that the light passes through. (Roughly...again, it gets complicated in real lens designs, just as with focal lengths.)

The bigger that hole, the more light gets through -- obviously. But the image gets spread out more, too, leaving less and less of it in focus and the out-of-focus areas more smeared out. It's all a matter of very simple geometry, and any introductory textbook will have illustrations that make it obvious and intuitive.

When determining proper exposure, what matters is how much light hits the sensor / film / whatever. And, again because of the geometry, it so happens that, even between lenses of different focal lengths, the ratio between the focal length and the physical size of the aperture is what determines how much light makes through the opening. A lens twice as long needs a hole twice as big to let through the same amount of light.

That ratio is expressed as the f/ number, and it's simply the focal length divided by the size of the aperture.

A 50mm lens at f/4 has a 12mm hole in the middle. So does a 24mm f/2 lens, and a 100mm f/8 lens, and a 200mm f/16 lens.

So, the bigger the f/ number, the bigger the hole you need. But you also need a bigger lens to focus the light over the whole area of that hole...and that's where things get expensive.

A 50mm f/1.0 lens has an aperture the same size as the focal length. A 50mm f/0.7 lens has a 70mm aperture, even bigger than the length of the focal length. That requires some really funky tricks with the geometry of the lenses, a hell of a lot of very high quality glass...and, even still, the results are decidedly soft.

I recently had a chance to buy a mint-condition Canon 50mm f/1.0L for $4,000. I turned it down. It's a much softer lens than the 50mm f/1.2L, which in turn is slightly softer (or, at least, no sharper) than the 50mm f/1.4. In low light, I'll get much better results with an additional stop of ISO than with that one extra stop of aperture, meaning the only remaining reason is for the super-shallow depth of field. But the depth of field is so shallow full open at f/1.0 that it's never actually sharp. You could just as easily shoot either of the other lenses wide open and apply a gaussian blur in post-production and get something that looks almost identical. Or, you could shoot at f/1.4 and smear some vaseline on a filter. Those extra thousands of dollars buys a hell of a lot of vaseline....

Cheers,

b&

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A large aperture lens is much harder to make sharp than a small aperture lens as that large aperture and resulting front element can capture light from an in-focus point-source of light at some relatively wide ranging angles - much more than at smaller apertures. For the in-focus areas to be sharp, the lens then has to refocus all of these different angles of light onto the same point on the sensor. Smaller apertures are easy - not many different angles to cope with, and a much smaller front element to design and manufacture. And tiny apertures (pinholes) have as close to just one angle as to mean there's no focusing or lens elements required. This is why large aperture lenses such as the EF 50/1.0 have a very dreamy look to them when used wide open.

And other than the technical difficulties of making the glass focus all that light onto one spot, another limit is the lens mount itself blocking some of that light. The EF mount has a larger diameter than the Nikon mount, which is why the largest production EF lens aperture was f1.0, whereas the largest F mount lens aperture was f1.2. Obviously this changes with a smaller sensor and a smaller flange distance, but it is still a limiting factor.

Why APS-C over m43 ? The difference in dof is tiny. For example, if I compare the NEX with 50mm f/1.8 vs the olympus with 45mm f/1.8 at 6 foot , I get .28ft for m43 vs .3ft for the Sony. If I adjust the to-subject distance so that the subject is framed the same way, I get 0.26ft dof for the Sony -- a slight advantage but nothing to write home about.

OP is right that the new Olympus models have closed the gap in image quality, this is largely due to them sourcing their sensors from Sony who currently have a decisive lead in sensor technology.